Occurrence of human papillomavirus (HPV) type replacement by sexual risk-taking behaviour group: Post-hoc analysis of a community randomized clinical trial up to 9 years after vaccination (IV)

Oncogenic non-vaccine human papillomavirus (HPV) types may conceivably fill the vacated ecological niche of the vaccine types. The likelihood of this may differ by the risk of acquiring HPV infections. We examined occurrence of HPV types among vaccinated and unvaccinated subgroups of 1992-1994 birth cohorts with differing acquisition risks up to 9 years post-implementation of HPV vaccination in 33 Finnish communities randomized to: Arm A (gender-neutral HPV16/18 vaccination), Arm B (girls-only HPV16/18 vaccination and hepatitis B-virus (HBV) vaccination of boys), and Arm C (gender-neutral HBV vaccination). Out of 1992-1994 born resident boys (31,117) and girls (30,139), 8,618 boys and 15,615 girls were vaccinated, respectively, with 20-30% and 50% coverage in 2007-2009. In 2010-2013, 8,868 HPV16/18 and non-HPV vaccinated females, and in 2014-2016, 5,574 originally or later (2010-2013) HPV16/18 vaccinated females attended two cervical sampling visits, aged 18.5 and 22-years. The samples were typed for HPV6/11/16/18/31/33/35/39/45/51/52/56/58/59/66/68 using PCR followed by MALDI-TOF MS. HPV prevalence ratios (PR) between Arms A/B vs. C were calculated for Chlamydia trachomatis positives (core-group), and negatives (general population minus core group). At both visits the vaccine-protected HPV type PRs did not significantly differ between the core-group and non-core group. Among the vaccinated 18-year-olds, HPV51 occurrence was overall somewhat increased (PRcore = 1.4, PRnon-core. = 1.4) whereas the HPV52 occurrence was increased in the core-group only (PRcore = 2.5, PRnon-core = 0.8). Among the non-HPV vaccinated 18-year-olds, the HPV51/52 PRs were higher in the core-group (PRcore = 3.8/1.8, PRnon-core = 1.2/1.1). The 22-year-olds yielded no corresponding observations. Monitoring of the sexual risk-taking core-group may detect early tendencies for HPV type replacement.